Re: 2.4 vm, program load, page faulting, ...

wind-lkml
2003-03-17T17:26:51Z

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On Mon, Mar 17, 2003 at 06:12:46PM +0100, wind-lkml@cocodriloo.com wrote:
> On Mon, Mar 17, 2003 at 07:50:04PM +0300, Alex Tomas wrote:
> > >>>>> wind (w) writes:
> >
> > w> On Mon, Mar 17, 2003 at 11:01:31AM -0500, Rik van Riel wrote:
> > >> On Mon, 17 Mar 2003, William Lee Irwin III wrote:
> > >> > On Sat, 15 Mar 2003, Paul Albrecht wrote:
> > >> > >> ... Why does the kernel page fault on text pages, present in
> > >> the page > >> cache, when a program starts? Couldn't the pte's for
> > >> text present in the > >> page cache be resolved when they're
> > >> mapped to memory?
> > >> >
> >
> > w> You should ask Andrew about his patch to do exactly that: he
> > w> forced all PROC_EXEC mmaps to be nonlinear-mapped and this forced
> > w> all programs to suck entire binaries into memory... I recall he
> > w> saw at least 25% improvement at launching gnome.
> >
> > they talked about pages _already present_ in pagecache.
>
> I wonder if this could be done by walking and faulting
> all pages at fs/binfmt_elf.c::elf_map just after do_mmap...
> will try it just now :)

OK, this is not tested, since I'm compiling it now... feel free
to correct :)

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--- orig/fs/binfmt_elf.c Mon Mar 17 18:26:59 2003
+++ work/fs/binfmt_elf.c Mon Mar 17 18:26:31 2003
@@ -259,12 +259,23 @@ create_elf_tables(struct linux_binprm *b
static inline unsigned long
elf_map (struct file *filep, unsigned long addr, struct elf_phdr *eppnt, int prot, int type)
{
- unsigned long map_addr;
+ unsigned long map_addr, pgoff;
+ struct mm *mm;

down_write(&current->mm->mmap_sem);
map_addr = do_mmap(filep, ELF_PAGESTART(addr),
eppnt->p_filesz + ELF_PAGEOFFSET(eppnt->p_vaddr), prot, type,
eppnt->p_offset - ELF_PAGEOFFSET(eppnt->p_vaddr));
+
+ /* preload elf image */
+
+ mm = current->mm;
+ addr = ELF_PAGESTART(addr);
+ for(pgoff = 0; pgoff < eppnt->p_filesz;){
+ do_mmap_pgoff(mm, filep, addr, PAGE_SIZE, prot, type, pgoff);
+ addr += PAGE_SIZE;
+ pgoff += PAGE_SIZE;
+ }

up_write(&current->mm->mmap_sem);
return(map_addr);